Centrifugal casting



July 6, 1937. D. J. CAMPBELL 2,085,726

GENTRIFUGAL CASTING Filed Feb. 2, 1931 5 Sheets-Sheet l III I lllll IHII! i I A Longld (1Com bell 1 M f m 2 ommL July 6, 1937.

CENTRIFUGAL CASTING Filed Feb. 2, 1951 5 Sheets-Sheet 2 27 45 14 Tii 27 y 20 v @Iomu D. J. CAMPBELL 2,085,726

July 1937. D. J. CAMPBELL CENTRIFUGAL CASTING Filed Feb. 2, 1951 5 Sheets-Sheet 5 Patented July 6, 1937 UNITED STATES CENTRIFUGAL CASTING Donald J. Campbell, Muskegon Heights, Mich., assignor to Campbell, Wyant & Cannon Foundry Company, Muskegon Heights, Mich a corporation of Michigan Application February 2, 1931, Serial No. 512,792

' 5 Claims.

This invention relates to a method of casting a composite construction of cast iron with an outer formed member of sheet metal which may be of steel or the like, and the product obtained with such method; and one of the articles of manufacture which can be made to great advantage using said process or method of casting is an automobile brake drum wherein an outer preformed shell of steel or the like is equipped with an inner braking ring or band of cast iron inseparably joined therewith, with the accomplishment of inner wearing surface of cast iron for the brake drum and an outer housing therefor of steel which is not of the breakable character of cast iron and is therefore tougher and more durable to withstand strains while the inner band of cast iron is of far better character than steel to withstand friction and wear, the composite construction having the necessary quality of light weight.

It is a primary object and purpose of the present invention to produce a process or method of composite casting of cast iron with steel, melted iron being applied to a rapidly rotating outer steel shell, and at the inner side thereof to provide a band of cast iron of uniform thickness inseparably joined with the shell, the rapid rotation of the shell with the melted iron therein setting up centrifugal action which forces the melted iron with pressure against the inner side of the shell, thereby greatly aiding in the production of a complete fusing joinder of the iron and steel at all points of contact.

A further object of the invention is to apply the iron in a molten state and at a very high temperature to a shell of steel or the like which is heated in order that there may be fusion" to a considerable degree between the iron and the inner sides of the shell, and also that chilling the iron when it strikes the inner sides of the shell shall not take place; while in addition the shell will shrink upon and tightly engage the iron when it has solidified but with not too great a gripping force such as would produce undue or excessive strains in the composite product obtained.

A yet further object of the invention is to apply melted iron in alimited quantity to the inner side of the shell of steel and secure an inseparable fusing and permanent joinder of the cast iron band at the inner side of the shell or drum of steel, whereby the outer shell provides a sup-,

porting brake drum structure for carrying the cast iron band, and without changing or modifying the physical characteristics or properties of the two characters of metal thus inseparably and permanently bonded together by fusion.

A still further object of the invention is to direct the molten iron with force of gravity and particularly with the force and pressure due to centrifugal action against the inner wall of the shell; and further to provide the inner wall of the shell with a series of raised serrations, ribs, projections or points, all of which is of aid in effecting a complete fusion connection of the cast iron with the surrounding material of the-shell.

Many other objects and purposes than those stated will be apparent on understanding of the invention had from the following description, taken in connectionv with the accompanying drawings, in which,

Fig. 1 is an elevation illustrating one form of apparatus with which my method or process may be satisfactorily accomplished.

Fig. 2 is a fragmentary plan view thereof.

Fig. 3 is a fragmentary enlarged section through the outer portion of one form of brake drum having a cast iron inner lining produced with the process of my invention.

Fig. 4 is a fragmentary vertical section on the line 44 of Fig. 3.

. Fig. 5 is an enlarged vertical section substantially on the line 5--5 of Fig. 2 with the parts in closed position and in the position they occupy when the cast iron band is to be cast at the inner side of the brake drum shell.

Fig. 6 is an enlarged front elevation of the drum holding die and various parts associated therewith, parts being broken away and shown in section for better disclosure of the construction.

Fig. 7 is a vertical section, similar to that shown in Fig. 5, illustrating a different form of construction by means of which the process may be attained.

Fig. 8 is a horizontal section substantially on the plane of line 88 of Fig. '7, and

Fig. 9 is a fragmentary vertical section illustrating the manner in which the molten iron is directed downwardly and in opposition to the direction of rotation of the sheet metal outer shell of the drum.

Like reference characters refer to like parts in the different figures of the drawings.

In the construction of the apparatus shown and by means of which the process may be carried out, a supporting pedestal l is used to carry an electric motor 2 on the shaft of which is a drive pulley 3, driving an endless belt 4 which passes around a driven pulley 5 at one end of a driven shaft 6, rotatably mounted on and above the pedestal l in bearings l which may be water cooled in practice through water circulating therethrough, carried by pipes indicated at 8. The shaft 6 at the end opposite where the pulley 5 is located extends beyond the adjacent bearing 1 and may be enlarged as indicated at 6a terminating in an annular flange 9.

A ring III of flat metal has a central opening to the pedestal. The ring In is located vertically and to it an annular housing |2 of sheet metal is secured, together with an annular hollow tubular burner I3 to which gaseous fuel may be continuously carriedthrough inlet pipes l3a, the purpose of which will be hereafter described. The shell l2 serves as a housing for the burner |3 and is of channel shape in cross section with a vertical web secured to the ring l8, and spaced apart horizontal annular flanges between which the burner I3 is located; and the burner at the open side of the housing is provided with a continuous series of small openings for the escape of the fuel which is to be burned as it escapes to produce heat.

A die M of suitable heat resisting material is formed with a cylindrical integral neck |5 which extends toward the flange 9 and terminates in an annular flange which is bolted directly to the flange 9 of the shaft 6. The die is of cylindrical annular form and at its outer side is surrounded by metal bands I6 and H as shown. The die at its inner side is formed with a cylindrical shallow recess thereby providing a continuous annular flange 8 for the die around the recess in which the sheet metal outer member of the brake drum is to be seated. The die is also provided with a plurality of spaced apart openings Hi therethrough which join with other spaced apart grooves 20 at the inner side of the flange I8 of the die; and the openings l9 are provided with sides inclined at an angle to the axis about which the die rotates, as indicated in Fig. 6, and the passages 28 are likewise inclined in the same manner, whereby the burning fuel from the burner 3 projecting into said passages i9 and 20 is accelerated in its movement through said passages and the products of combustion at very high temperature are directed against the outer walls of the brake drum shell seated in the die and impact thereagainst heating the shell and maintaining it at a desired high temperature.

The brake drum shell of sheet metal of suitable composition such as steel or the like is rolled or pressed or otherwise preformed into shape before the cast iron inner band is to be applied thereto. It has a web 2| joined with which is a continuous annular cylindrical drum flange 22 which terminates in an outturned annular lip 23. Many brake drums are of this character of construction, though I have designed another, as will be later apparent, in which a flange is turned inwardly from the free edges of the part 22 instead of outwardly. The web 2| of the shell has a central opening around which a plurality of spaced stud openings are made through which the bolts which attach the drum to an automobile wheel may be subsequently passed. The die I4 is equipped with a plurality of pins 24 which project through the openings in the web 2| to locate the drum shell in proper position with reference to the die and cause it to rotate with the die. In preparation for use in my process also the inner annular surface of the cylindrical drum flange 22 maybe serrated continuously around the same as indicated at 25; and while the serrations are showngas' parallel to the axis of the drum, it is to be understood that any form of s'erration or in fact anything which provides a consecutive series of raisedpoints or lines separated by depressions such as may be accomplished by knurling, threading or the like may be used for the same purpose as an equivalent of the serrations shown at 25.

The drum shell formed as shown and described ward movement. To accomplish this the die l4 is recessed around its central portion and a plate 25 seated and secured in the recess inwhich a plurality of sliding jaws 21 are slidably mounted to move in andout on radii of the plate26. The jaws at their inner sides are grooved or threaded to engagewith spiral threads and grooves on a circular plate 28 mounted within the recess inside of the plate 26, which plate 28 is connected with a stud shaft 29 provided with a squared outer end whereby it may be turned to thereby radially move the jaws 21 in Or out and when moved outward the ends of the jaws, which are inclined as shown in Fig. 5, bear against the edges of the web 2| of the drum around the central opening therethrough. It is therefore evident that the drum shell is securely yet detachably held in the die and must move with the die in its rotation when the shaft 6 is driven.

A base support or bracket 30 is secured to the pedestal and extends therefrom at the outer end of which a vertical post 3| is connected. A supporting arm 32 is mounted for turning movement at the upper end of the post 3| and carries a stack 33 of suitable heat resistant material at the lower end of which is a laterally projecting arm 34. This stack may be of any desired height and at its upper end portion is provided with a recess or cavity 35 in which a quantity of molten iron may be placed. From the recess or cavity a runner passage 36 extends downwardly through the stack and thence laterally through the arm 34 and at the end of the arm is widened and extended downwardly at an angle as indicated at 31 (Figs. 5 and 9). A stopper 38 may be used between the lower end of the iron receiving cavity 35 and the runner 36.

On an arm 33 extending upwardly from the arm 32 a spider comprising a central sleeve and a plurality of radially extending arms 4!) is secured. A ring 4|, preferably T-shape in cross section, has a plurality of cylindrical plugs or bosses 42 extending therefrom which pass into openings made through sleeves at the outer ends of the arms 40 to bear against compression springs 43 mounted in said sleeves as shown. A second ring or ring die 44 is located inside of the first ring and is joined therewith by means of an annular ring 45 permanently secured at the inner side of the ring 44 and extending within the outer ring 4| being equipped with an outturned annular lip 45a which engages with a flange of the ring 4|. Suitable antifriction ball bearings 46 are located between the two rings 4| and 44.

When the arm 32 with the attached devices described thereon is swung to inner position, the inner ring die 44 bears against the outturned lip 23 of the drum shell, rotates therewith and is pressed thereagainst by spring pressure, while the lower end of the runner 3! lies within the annular cylindrical flange 22 of the drum shell and above the same. Withdrawing the stopper 38 permits the molten metal to pass down the runner 36 and it is projected outwardly, as at 41, Fig. 9, and downwardly at an angle to the'inner serrated surface 25 of the drum shell and preferably in a direction in opposition to the direction of rotation of the shell; and with the drum rotating, the molten iron forms a continuous annular band 48 at the inner side of the cylindrical outer flange 22 of the drum through centrifugal action. This pouring process continues for a space of time ranging from 3 to 5 seconds, depending upon the heat of the molten metal and the thickness of the casting desired, and I have found it convenient to rotate the drum at about 1100 R. P. M. Running at this speed, and using a brake drum such as is usually employed on the conventional small car, approximately 4200 feet of surface is subjected to the impact of the metal in the course of a minute, and the result is a thin. ribbon-like distribution-of the molten metal within the inner braking surface of the drum. If a drum of greater diameter, or other larger article is being processed, the speed may be decreased, it being apparent that the heat of the metal, the thickness of casting desired, and the speed of rotation are all factors that may be varied to secure the particu-,

lar result desired in a specific case. The arm 32 is provided with a stop to limit its outward movement and it and the bracket 30 have holes 49 (Fig. 2) therethrough through which a pin may be dropped to hold the device at its inner position.

It is evident that such depositing of the melted iron as described results in a continuous radial increase in the thickness of the band of melted iron until the de'siredamount has been deposited; that such band of melted iron is of uniform thickness due to the centrifugal action and forces generated thereby, and that there is an intimate forced contact of the melted iron with the inner side of the shell, which at the temperatures of the melted iron and shell hereafter stated, causes the intimate permanent joinder by fusion of the two metals, with an inseparable bond at their con tacting surfaces at all points; but because of the limited amount of the melted cast iron used with a shell, and its manner of deposition therein, the outer shell is not affected except at its inner surface where the fusion joinder is made, and there is no change in the physical form or properties of the outer shell during the carrying out of the process.

The drum shell, before it is placed within the die It, is thoroughly cleaned at its inner surface 25, and may in some cases be nickel or copper plated or plated with various other metals to insure such surface against oxidizing while the drum is being heated, or in some cases a coating may be used to protect against oxidizing or a composition used that will lower the fusing point on the metal contact surfaces, assuring a better interlocking or fusion between the drum shell and the cast iron band. Various compounds, such as red lead, aluminum, thermit or other metal fluxes may be used as well known in the art of welding.

The drum shell, either within the die or before it is placed within the die, is heated to a high degree of temperature the maximum of which should not exceed approximately 1500 F. This maximum temperature is governed in large measure by the condition that the drum shell has to serve as the support and backing against which the molten iron bears, and has to withstand centrifugal forces tending to distort the shell; and too high temperatures at or approaching which the material of the shell would melt or soften too greatly must be avoided. The range of temperatures in heating the shell is governed chiefly by the temperature of the molten iron which has a somewhat limited permissible range, but it has been found that for the best and most uniform results the minimum temperature should be at least 1200" F-., with the molten iron at substantially 2800 or 2850 F.; but that at 3000 F.,

aoamaa for the molten iron this minimum temperature may be lowered considerably, as to 800 F., and under some conditions even lower. It is practical to place the cold drum within the die and heat it from the burner IS, the heated products of combustion being projected against the drum and heating it to the required temperature in a very short time, or the drum may be previously heated in a suitable furnace to approximately the desired temperature, placed in the die. The die serves to hold the drum to its form as otherwise, particularly when heated to high temperature, the rotation of the drum especially at high speeds has a tendency to enlarge or distort the drum through centrifugal action.

The temperature of the molten metal is very high, reaching at times 3000 F. The range of temperature permissible for the molten iron is not so great as that permitted for the wrought steel shell. The lowest temperature for the molten iron should not be less than substantially 2700 Fahr. Under the centrifugal action of the column of the molten metal in the runner passage 36 whereby it is carried with considerable force against the serrated surface 25, and with said surface heated to a high degree of temperature as described, there is a fusion of the molten metal and the adjacent surface portions at the inner side of the drum flange 22 and, particularly, there is a fusion of the higher portions of the serrations with the molten metal. As soon as the desired quantity of molten metal has been deposited within the drum shell the heat from the burner i3 is discontinued if the burner has been used, so that the inner cast band 48 and the drum shell cool, the molten metal solidifying and the drum shell contracting thereon as the same cools.

The method may be practical with diiferent apparatus. In Figs. 7 and 8, a hollow annular metal covering 50 is lined with heat resisting material 5|, within which an annular burner 52 is mounted, fuel being led thereinto through pipe 52a, and projected-outwardly and burned at the ends of nozzles 53 located around the inner side of the burner. This device is permanently secured to a bracket Ila extending. from the pedestal I and is located in axial alignment with the rotating shaft 6, to the flange 9 of which a drum shell holding member is secured, which includes a head 54, carrying pins 55 similar to the pins 24 previously described, with a flanged cylindrical neck extending therefrom which is permanently secured to the flange 9 as shown. The brake drum shell is located as to position by placing the openings through the web thereof over the pins 55, and is locked in place by a key member 51 having an outer head 58- and a series of projections 59 at its inner end which pass through slots 60 in the head 54 previously described, and may then be turned so as to bring the outer head 58 against the web SI of the drum shell to hold the same in position and cause its rotation with the shaft 5.

The drum shell in this case, in addition to the web GI has an annular drum flange 62 which is serrated or grooved on its inner side with continuous annular spaced apart grooves, as indicated at 63, and the drum flange 62 terminates in an inturned annular lip 64.

The lip 64 forms a retainer for the molten metal which is deposited against the serrated, grooved or roughened inner surface 63, andthere is no need for a ring die like or equivalent to the ring 44 which, in the previously described structure, holds the molten metal from flowing outwardly. The molten metal is deposited against the inner surface of the drum shell the same as before, the drum either having been previously heated or heated after it is placed upon the pins 55 to the required degree of temperature, and maintained at this temperature until the molten metal has beendeposited. This form of apparatus may be used where the drum shell is of heavier material so that it will not lose its shape from centrifugal action at high speeds of rotation; or where the rotation of the drum is at lesser speeds; or where the temperature of the molten metal deposited therein is of lesser temperatures than the maximum. In all cases, however, the drum shell at its inner side is cleaned and is otherwise treated if necessary to prevent oxidizing and scaling under;the temperatures to which it is heated. The molten metal is deposited preferably under the combined influence of gravity and hydrostatic pressure and, preferably, in a direction opposite the direction of rotation of the shell and, with the pressure produced by centrifugal action and with the high temperatures of the shell and melted metal there is ac complished fusion of the shell at its inner sides with the molten metal and a contraction of the shell against the cast iron wearing ring or band within it on cooling.

The method and process described is one of great practical utility in connection with brake drums. All of the advantages in the matter of strength, toughness and the like of steel are combined with all of the advantages of cast iron as a wearing and braking surface, and the disadvantages of each if used alone are eliminated. The

'requisite and necessary lightness in weight is attained which would be impossible if cast iron alone was used and all of the advantages of cast iron in any of its various compositions which may be used for a braking surface are secured. The invention has been extensively tested and has proven completely satisfactory in all respects. Herein by wrought steel or the like is meant that the steel has been subjected to physical working. The invention is to be understood as comprehensive of what is defined in the claims and not limited in any sense to particular apparatus used or otherwise than as required by the claims defining the invention.

I claim:

1. The method of producing brake drums and the like which consists in the following steps; first, covering the inner peripheral surface of a wrought steel brake drum shell with an airexcluding coating; second, heating the coated drum shell to a temperature of above 1200 F.; third, rotating the heated shell about its axis; and fourth, while the heated drum shell is rotating, depositing against the coated inner peripheral surface thereof, molten iron, the temperature of which is above the melting temperature of the steel forming the drum shell.

2. The herein described method of brake drum production which consists in providing a preformed wrought steel shell, heating the shell while wholly surrounded by air to a temperature be tween 1200 and 1500 F., rotating the heated shell about its axis, protecting the inner peripheral surface of the steel shell against oxidizing while it is being heated and depositing molten iron in said drum while it is rotating in the atmosphere, the temperature of the molten iron being in a range between 2700 and 3000 F.

3. The herein described method of brake drum production which consists in producing a wrought steel drum shell, heating said shell while the same is entirely surrounded by air to a temperature between 1200 and 1500 F., protecting the inner side of the drum against oxidizing when the same is heated, rotating said shell in the atmosphere and depositing molten iron at a temperature above 2700 F. into the rotating shell in a quantity to provide a relatively thin continuous layer over the inner side of the shell when evenly spread thereover, the rotative speed of the shell being such that the molten metal spreads in a continuous, even thickness band over the inner side of the shell and the high temperature of the molten iron deposited in the shell causing said iron to remain liquid for a time interval suflicient that all impurities lighter than the molten iron pass radially inward therethrough to the inner side of said iron.

4. The herein described method of brake drum production which consists in preforming a thin wrought steel cylindrical shell, heating said shell while the same is entirely surrounded by air to a temperature approximating 1200 as a minimum and 1500 as a maximum, maintaining the inner side of the shell against oxidizing while the same is being heated, and afterward rotating said drum in the air and depositing molten iron in the rotating shell at a temperature above the melting point of the steel used and not exceeding 3000 F., said temperature of the molten iron being sufliciently high above the melting point of said iron that it remains liquid for an appreciable time interval between the time it is deposited and its solidification whereby, through centrifugal action, the heavier liquid molten iron presses into intimate contact with the steel shell and impurities are carried radially inward through the liquid molten metal, and said high temperature molten iron causing the steel shell to be raised to a temperature exceeding the melting point of the steel.

5. The method of producing brake drums and against the inner peripheral surface thereof, in

such quantity as to provide a relatively thin continuous layer of molten iron spread over the inner periphery of the shell, the rotational speed of the shell being such that the molten metal spreads and flows into a continuous band of generally even thickness over the entire inner periphery of the drum shell; the high temperature of the molten iron deposited in the shell causing the iron to remain liquid for a time suflicie'ntly long to permit impurities lighter than the molten iron to pass radially inward therethrough to the inner side of the iron layer before solidification of the iron.

DONALD J. CAMPBELL. 

